java中next与nextLine的用法

import java.util.*;

public class Retirement2
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);

System.out.print("How much money will you contribute every year? ");
double payment = in.nextDouble();

System.out.print("Interest rate in %: ");
double interestRate = in.nextDouble();

double balance = 0;
int year = 0;

String input;

// update account balance while user isn't ready to retire
do
{
// add this year's payment and interest
balance += payment;
double interest = balance * interestRate / 100;
balance += interest;

year++;

// print current balance
System.out.printf("After year %d, your balance is %,.2f%n", year, balance);